MESOSCALE DISCUSSION 1738
   NWS STORM PREDICTION CENTER NORMAN OK
   1109 AM CDT WED SEP 28 2016

   AREAS AFFECTED...SRN MD...MUCH OF VA...CENTRAL NC...

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 281609Z - 281715Z

   PROBABILITY OF WATCH ISSUANCE...60 PERCENT

   SUMMARY...A GRADUAL INCREASE IN SEVERE POTENTIAL IS FORECAST TO
   OCCUR ACROSS THE VA/NC VICINITY EARLY THIS AFTERNOON...WHICH MAY
   REQUIRE WW ISSUANCE.

   DISCUSSION...LATEST SURFACE ANALYSIS SHOWS A PRIMARY SURFACE LOW
   OVER SRN INDIANA...WITH A RETREATING DAMMING FRONT/EFFECTIVE WARM
   FRONT LYING NE-SW ACROSS CENTRAL VA.  WITH A 1030 MB HIGH INVOF NRN
   ME RIDGING SWWD IN LEE OF THE MOUNTAINS...THE FRONT MAY BE HINDERED
   FROM MAKING SUBSTANTIAL NWD/NWWD PROGRESS THROUGH THE AFTERNOON.

   MEANWHILE ALONG AND S OF THIS BOUNDARY...A VERY MOIST LOW-LEVEL
   AIRMASS IS IN PLACE...WITH DEWPOINTS IN THE LOW 70S ACROSS THE NC
   PIEDMONT AND INTO SERN VA.  SOME THINNING OF CLOUD COVER EVIDENT IN
   THE LATEST VISIBLE LOOP SE OF THE FRONT WILL ALLOW MODEST HEATING TO
   CONTINUE -- EVENTUALLY YIELDING 500 TO 1000 J/KG MIXED-LAYER CAPE
   ACROSS CENTRAL VA...AND IN EXCESS OF 1000 TO 1500 J/KG FARTHER SSW
   INTO NC.  

   LARGE-SCALE FORCING FOR ASCENT ALOFT SHOULD REMAIN LIMITED ACROSS
   THE AREA...WITH NEUTRAL TO WEAKLY RISING HEIGHTS ACROSS THE REGION
   AS THE MAIN UPPER SYSTEM DRIFTS SSEWD ACROSS INDIANA. 
   HOWEVER...WEAK LOW-LEVEL WARM ADVECTION AND MORE FOCUSED ASCENT
   INVOF THE AFOREMENTIONED SURFACE FRONT SHOULD SUPPORT STORM
   DEVELOPMENT -- PERHAPS WITHIN THE NEXT 1-2 HOURS IF SOME CAM
   SOLUTIONS /INCLUDING THE HRRR/ ACCURATELY DEPICT THE EVOLVING
   SCENARIO.  SOME INCREASE IN CU DEVELOPMENT/WEAK RADAR ECHOES NOW
   INDICATED INVOF THE VA/NC BORDER MAY LEND CREDENCE TO THE HRRR
   SCENARIO -- WHICH COULD NECESSITATE CONSIDERATION OF WW ISSUANCE
   SOONER THAN AN OTHERWISE MID-AFTERNOON EXPECTATION FOR CONVECTIVE
   INCREASE.

   WITH SLY/SELY LOW-LEVEL FLOW ACROSS THE AREA S OF THE FRONT EXPECTED
   TO GRADUALLY BACK/INCREASE SLIGHTLY...LOW-LEVEL SHEAR -- BENEATH 40
   TO 50 KT MID-LEVEL SWLYS -- WILL BE FAVORABLE FOR ROTATING UPDRAFTS.
    WHILE SOMEWHAT LIMITED INSTABILITY -- PARTICULARLY ACROSS VA --
   SHOULD LIMIT HAIL RISK...LOCALLY DAMAGING WINDS WILL BE POSSIBLE
   ALONG WITH A FEW TORNADOES.  GREATEST TORNADO RISK MAY EVOLVE ALONG
   THE FRONT -- PARTICULARLY WITH ANY STORMS WHICH BECOME ANCHORED/MOVE
   NEWD ALONG THE VORTICITY-RICH ZONE INVOF THE BOUNDARY.

   ..GOSS/HART.. 09/28/2016


   ATTN...WFO...AKQ...LWX...RAH...RNK...

   LAT...LON   38427679 37897630 36807665 36047778 35807832 35997925
               36407963 37127942 38087815 38427679